Gov. Robert Bentley talks with reporters outside the Capitol in Montgomery, Ala., Wednesday. Bentley said a federal judge left most of the state's tough new immigration law in place, and it's still the strongest in the nation.

A federal judge’s ruling in Alabama Wednesday raises the possibility that, after being repeatedly rejected by courts across the country, a controversial provision that police check the immigration status of people who might be illegal immigrants could be enforced for the first time.

Several states have passed anti-illegal immigration bills with similar statutes, starting with Arizona's SB 1070 last year. But each law has been put on hold by the courts until now. Chief US District Judge Sharon Blackburn on Wednesday rejected some parts of Alabama's far-reaching bill against illegal immigration. But she upheld the section of the law dealing with residency-status checks during routine stops.

For law enforcement, which has repeatedly opposed such laws, the ruling is raising questions about how such a mandate can be enforced – and whether it will lead to lawsuits over allegations of civil-rights violations.

Appeals from opposition groups are certain, and some experts say the Alabama ruling makes it increasingly likely that the issue will end up before the US Supreme Court. The Arizona case has already been appealed to the Supreme Court, though the court has not yet decided whether it will take the case.

In her ruling, Judge Blackburn also upheld a requirement that Alabama public schools check the immigration status of students. She blocked other parts of the law, including the prohibitions against illegal immigrants applying for work or penalties for knowingly concealing, harboring, or transporting illegal immigrants in the state.

“It would be impossible to call it a victory for either side,” says Paul Horowitz, a constitutional law expert at the University of Alabama’s law school in Tuscaloosa. The overall ruling shows that “the state can parallel federal law but can’t innovate immigration law.”

For law enforcement, however, the ruling was a defeat.

Police authorities say the law’s wording makes them ripe for lawsuits. As written, the law allows police officers to act on “reasonable suspicion” and require people to produce proof of legal residency. The law also allows people to sue law-enforcement agencies if they feel the agencies aren't doing what the law requires.

The problem is that no database exists that could easily, or even adequately, verify the numerous documents that show legal status, from work visas to border crossing cards to birth certificates. That makes the law virtually unenforceable, says Professor DeSipio.

“It just doesn’t work,” he says. “A database can have a lot of false positives. In a workplace, that’s not a problem because the employer can give a person a certain amount of time to correct the problem. But parked on the side of a highway in Alabama, there’s not much you can do.”

Local law-enforcement officials in Alabama have protested the bill since Gov. Robert Bentley (R) signed it into law June 9. They say that they do not have the training or equipment to verify legal status. They also say the new duties will squeeze departments already facing cuts.

It is not clear “whether any kind of resources will follow the political will or [whether the law-enforcement provision] was meant to be a substantially symbolic statement,” says Professor Horowitz. “This is still going to be a real burden on state and local resources. If the state is serious about the law, it is going to have to provide resources."

In a statement, Governor Bentley said the provisions Blackburn allowed meant Alabama has “the strongest immigration laws in this country,” and he added that the state will likely appeal to a higher court to uphold the provisions blocked by Wednesday’s ruling.

He said the law “was never designed to hurt fellow human beings.” However, he said the bill “would not have been necessary if the federal government had done its job and enforced the laws dealing with this problem.”

Alabama ranks 20th in the nation in terms of number of illegal immigrants, according to the Pew Hispanic Center. Illegal workers in Alabama represent 4.2 percent of the state’s labor force.

The size of the illegal-immigrant population in the state has increased rapidly during the past 10 years. Between 2000 and 2010, the number of illegal immigrants in Alabama rose 380 percent, from 25,000 to 120,000 according to Pew. Today, illegals represent 2.5 percent of the total state population.